A rope used to move a cage of an elevator up and down is fatigued and/or worn and as a result has its constituent steel wires broken one after another. Accordingly, after the elevator has been installed, the elevator undergoes a periodical inspection to confirm which portion the steel wires have broken or how many of the steel wires are broken visually or with a measuring instrument to evaluate the rope for safety.
In recent years, as hoists are reduced in size and sheaves are reduced in diameter, a resin coated rope for example having a circumference coated with thermoplastic polyurethane elastomer or a similar excellently elastic resin is increasingly used. An elevator with a resin coated rope receives power from a hoist and transmits it to a cage through the rope via the coating of resin, and accordingly, the coating of resin is required to have a large mechanical strength, and a satisfactory friction characteristic for the hoist's sheave. Accordingly, the elevator with the resin coated rope entails a periodical inspection conducted not only to confirm whether the rope has its steel wires broken but also to confirm whether the rope has its coating of resin degraded.
Whether a resin coated rope has its coating of resin degraded is detected in a method proposed for example as follows: whether a steel wire that configures the rope and a sheave have established electrical conduction therebetween is detected to detect whether the coating of resin is damaged (see Japanese Patent Laying-Open No. 2009-143678 (PTD 1) for example). Furthermore, whether a urethane roll circumferentially coated with polyurethane resin is degraded is non-destructively detected in a method proposed as follows: the urethane roll's indentation hardness is measured to obtain how much in degree the indentation hardness as measured is different from that of the urethane roll as measured when it was an unused product, and therefrom whether the urethane roll is degraded is detected (see Japanese Patent Laying-Open No. 2002-062232 (PTD 2) for example).